1. Field of the Invention
The present invention relates to a battery module, and in particular to a rechargeable battery for constituting the battery module in which the internal battery resistance can be made small and the battery output can be increased.
2. Description of Related Art
FIG. 10 shows a conventional battery module made by connecting a plurality of rechargeable batteries and coupling them together as one so as to obtain the necessary power. In this battery module, a plurality of cells 41 (41a to 41j) made of sealed alkaline rechargeable batteries as shown in FIG. 11 are arranged side by side, with the long lateral walls of the battery cases 42 adjacent each other. End plates 52 are arranged against the outside of the cells 41a and 41j at both ends, and the two end plates 52 and 52 are bound together with binding bands 53 so as to couple the cells together as one piece.
For the cells 41, an electrode plate group 47, comprising positive electrode plates and negative electrode plates layered with intervening separators, thus constituting elements for electromotive force, is accommodated in a battery case 42 together with a liquid electrolyte, and the open end of the battery case 42 is closed with a lid 46 provided with a safety vent 45. From the upper end at one side of the positive electrode plates forming the electrode plate group 47, leads 49 extend upward and are connected to a positive electrode terminal 43 above them, and similarly, from the upper end of the other side of the negative electrode plates, leads 49 extend upward and are connected to an negative electrode terminal 44 above them. The positive electrode terminal 43 and the negative electrode terminal 44 are attached to the lid 46.
The positive electrode terminals 43 and negative electrode terminals 44 of coupled neighboring cells 41 are connected by connection plates 51, thereby connecting all cells 41 in series. When the battery cases 42 are coupled, ribs 48, which protrude vertically from the long lateral walls of the battery cases 42, are abutted against each other, forming coolant passages running in the vertical direction along the long lateral walls of the battery cases 42 in the space between ribs 48. The cells 41a to 41j are cooled by flowing air through these coolant passages.
However, with the configuration for the cells 41 of this conventional battery module, leads 49 extend from a portion at the upper end on one side of the electrodes and are connected to the electrode terminals 43 and 44, and consequently, there were the problems that the internal resistance of the battery was large, because the average distance from the surface of the electrodes to the collector portions of the leads 49 was long, and that the power output was low, because the utilization rate of the electrode active material was low.
Moreover, because the terminals 43 and 44 protruding to the outside of the lid 46 are connected by connection plates 51, it is necessary to provide space for this connection at the upper end of the battery cases 42. Furthermore, since the connection portions are exposed, there is the problem that the space for installing this battery module cannot be made compact.
Moreover, in the portions where electrode pillars of the electrode terminals 43 and 44 extend through the lid 46, O-rings for providing a seal are usually placed only on the inner side of the lid 46, and there was the danger that electrolyte may leak during use of the battery.